In cardiac failure, continuous ambulatory electrocardiographic recording for 24 hours (Holter system) enables detection of 60 to 80% of complex ventricular arrhythmias, 15 to 40% of atrial arrhythmias and sudden death accounts for about 40% of fatalities but its causes are multiple and sometimes unrelated to arrhythmias. Abnormalities of cardiac structure, metabolic and neuro-hormonal changes and some drug therapies are implicated in the genesis of these arrhythmias, the management of which is discussed in two different situations with respect to the functional incapacity: in paucisymptomatic ventricular arrhythmias in patients with cardiac failure, class I antiarrhythmics and d-sotalol should be avoided and betablockers prescribed with caution; the indications of amiodarone have not yet been determined. When the arrhythmia is symptomatic (sustained ventricular tachycardia or ventricular fibrillation), class I antiarrhythmics are not effective enough in the prevention of sudden death; betablockers and amiodarone may give good results but should be compared with implantable defibrillators in the future. The multiplicity and complexity of the mechanisms of arrhythmias in cardiac failure, and the inadequate results obtained with classical antiarrhythmics necessitate the development of new antiarrhythmics based on blockade of non-selective channels probably activated in cardiac failure by the stretching of myocardial fibres.